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7A1–86 TRANSMISSION CONTROL SYSTEM (4L30–E)
f An intermittent or incorrect engine speed signal may
set a DTC P1870.
Test Description
The numbers below refer to the step numbers on the
diagnostic chart:
2. This test checks the indicated range signal to the
actual selected range. A faulty switch could set a
DTC P1870.
3. This test checks the torque converter for slippage
while in a commanded lockup state.
DTC P1870 Transmission Component Slipping
Step
1
Were you sent here from the "Powertrain On–Board Diagnostic
(OBD) System Check"?
2
1. Install the scan tool.
2. With the engine "off", turn the ignition switch "on".
NOTE: Before clearing DTC(s), use the scan tool to record "Freeze
Frame" and "Failure Records" for reference, as data will be lost
when the "Clear Info" function is used.
3. Record the DTC "Freeze Frame" and "Failure Records".
4. Apply the brake pedal.
5. Select each transmission range: D1, D2, D3, D4, N, R, and P.
Does each selected transmission range match the scan tool "TR
Switch" display?
3
Drive the vehicle in 4th gear while the TCC is engaged.
At any time is the "TCC Slip Speed" greater than 130 rpm for 8
seconds while the TCC is engaged?
Range Switch Logic Table
Action
Range Switch Pin
Range
g
Position
A
Park
ON
OFF
Reverse
ON
ON
Neutral
OFF
ON
D4
OFF
ON
D3
ON
ON
2
ON
OFF
L
OFF
OFF
Illegal
OFF
OFF
Illegal
OFF
OFF
Yes
Go to Step 2
Go to Step 3
Go to System
Diagnosis Charts
B
C
P(G)
OFF
ON
OFF
OFF
OFF
ON
ON
OFF
ON
ON
ON
OFF
ON
ON
OFF
OFF
OFF
ON
No
Go to OBD
System Check
Refer to
Driveability and
Emissions in
Engine section
Go to "Range
Switch Logic
Table"
Go to Diagnostic
Aids
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